Treatment of cancer patients with chemotherapeutic agents remains the primary method of treating systemic disease. There is a direct association between chemotherapeutic dose intensity and clinical response rate. However, increasing doses of chemotherapy have significant side effects including the widespread destruction of bone marrow hematopoietic precursor cells with concomitant destruction of peripheral myeloid and lymphoid cellularity. Thus, stem cell transplantation is used in conjunction with high dose chemotherapy, frequently in combination with growth factor support, to facilitate the recovery of the hematopoietic system following chemotherapy.
There are two general types of stem cell transplantation: allogeneic and autologous. In allogeneic transplantation, stem cells from a donor other than the patient are infused. This protocol carries a high mortality rate due primarily to graft-versus-host disease wherein the transplanted cells attack the patient""s own tissues. Autologous stem cell transplantation (or xe2x80x9cstem cell rescuexe2x80x9d) is a protocol wherein the patient""s stem cells are isolated prior to the high dose chemotherapy and subsequently reinfused. Because autologous transplantation does not result in graft-versus-host disease, the procedure related mortality is reduced compared to allogeneic transplantation. However, in a disease and stage dependent manner, autologous transplantation may result in the reinfusion of tumor cells from within the stem cell product.
Treatment with high-dose chemotherapy in conjunction with autologous bone marrow transplantation is used increasingly in patients with breast cancer. (See e.g., Myers, et al. Bone Marrow Transplantation, 13:449-454 (1994); Ghalie, et al. Biology of Blood and Marrow Transplantation, 1:40-46 (1995); Bezwoda, et al. J. Clin. Oncology, 13:2483-2489 (1995); Kennedy, M. J., J. Clin. Oncology, 13:2477-2479 (1995); To, et al. Blood, 89:2233-2258 (1997). However, a high relapse rate after high dose chemotherapy is still observed, especially in women with metastatic breast cancer. Vahdat, L. and Antman, K. H. (1995) p. 802. Baltimore: Williams and Wilkins. In most cases, failure to eradicate disease by the treatment regimen is the cause of disease recurrence. However, there is strong evidence from gene marking studies that tumor cell contamination of the bone marrow cells can also contribute to recurrence in cancer patients. Brenner, et al., Lancet, 341:85-86 (1993); Brenner, et al. Ann. N.Y. Acad. Sci. 716:204-215 (1993); Deisseroth, et al. Blood, 83:3068-3076 (1994); Sharp, J. G., J. Hematotherapy, 5:519-524 (1996). Tumor cells can be detected not only in the bone marrow of patients having advanced breast cancer (20 to 70%) but also in the bone marrow of patients with localized breast cancer (20% to 45%) using sensitive immunocytochemical analysis or reverse transcriptase-polymerase chain reaction (RT-PCR) assays (See e.g., Berger, et al., Am J Clin Pathol., 90:1-6 (1988); Mansi, et al., Br. Med. J. 295:1093-1096 (1987); Diel, et al., J. Clin. Oncol. 10:1534-1539 (1992); Porro, et al., Cancer, 61:2407-2411 (1988); Cote, et al., J. Clin. Oncol. 9:1749-1756 (1991).)
In order to avoid reinfusing the cancer cells into the patient undergoing high-dose chemotherapy in conjunction with autologous stem cell transplantation, practitioners have attempted to xe2x80x9cpurgexe2x80x9d bone marrow cells of their contaminating tumor cells. various approaches for the ex vivo tumor cell purging of stem cell products have been developed. The use of monoclonal antibodies against membrane antigens with cytotoxic drugs, toxins, phototherapy, and biological modifiers or cytotoxic drugs can reduce tumor contamination by 1 to 3 logs (Seiden, et al., J. Infusional Chemotherapy 6:17-22 (1996)). However, purging using cytotoxic drugs often leads to delayed engraftment (Rummel, et al., J. Hemotother. 3:213-218 (1994)). The selection of CD34+ hematopoietic progenitor cells has also been used to reduce tumor cell reinfusion, although demonstrating lower purging efficacy (1 to 2 logs). The clinical purging of breast cancer cells from bone marrow with 4-hydroperoxycyclophosphamide (4-HC) has been reported by Osborne et al. to improve clinical outcome (Osborne, et al., Cancer Res. 51:2706-2709 (1991)). However, the use of 4HC is not favored because 4HC is toxic to stem cells and delays neutrophil recovery. Furthermore, although 4HC results in approximately a 3 log purge of tumor cells, this is significantly less than the 5-log purge generally considered optimal to effectively purge tumor cells from a stem cell product. In another protocol, antibodies reactive with the tumor cells are conjugated to radioisotopes and have been demonstrated to purge tumor cells (Gibbons, et al). In this study, patients whose marrow was rendered xe2x80x9ctumor freexe2x80x9d following purging had a significantly improved survival compared to those whose marrow was not successfully purged.
Stem cell rescue, following myeloablative high dose chemotherapy with autologous bone marrow products has been predominately replaced with transplantation using mobilized peripheral blood stem cells (PSC). The use of PSC rescue results in a more rapid neutrophil recovery following high dose chemotherapy as compared to steady state autologous bone marrow transplantation (Bezwoda, et al., J. Clin. Oncol. 13:2483-2489 (1995); To, et al., Blood 89:2233-2258 (1997)). In addition it allows the use of stem cell products in patients with marrow aplasia due to radiation or who have extensive tumor contamination of the marrow.
Initially, it appeared the PSC products were free of tumor cells. However, more recent studies have demonstrated that cancer cells can also be detected in mobilized PSC products (Mapara et al. Blood 89:337-344 (1997)). This is a critical observation as gene marking studies have demonstrated that reinfused tumor cells can directly contribute to disease relapse and a poor clinical outcome. Whether all such contaminating tumor cells are capable of clonogenic growth is debatable and indeed it appears that only a subset of such tumor cells have clonogenic growth capacity. Nonetheless, in the cases of lymphoma, leukemia, breast cancer and neuroblastoma, at least some of the contaminating tumor cells have the capacity to grow clonogenically in vitro (Ross, et al., Blood 82:2605-2610 (1993)) as well in the patient. Although PSC products appear to have a reduced level of tumor cell contamination compared to the bone marrow, the potential for contaminating tumor cells to contribute to disease relapse is significant.
Seth et al. (Cancer Research 56:1346-1351 (1996)) disclosed that rAd-p53 may preferentially infect breast cancer cells compared to CD34+ mobilized peripheral stem blood cells. Chen et al. (J. Clin. Invest. 98:2539-2548 (1996)) disclosed a higher level of adenoviral-mediated reporter gene expression in breast cancer cells compared to bone marrow, peripheral blood and CD34+ cells, and disclosed the potential use of adenoviral vectors with tumor-selective promoters to detect and purge hematopoietic stem cell preparations.
As noted above, current protocols for the purging of stem cell populations have significant drawbacks. Thus, there is a need for new protocols for the effective purging of PSC products. This need and others are addressed by the instant invention.
The present invention provides a method to purge tumor cells from stem cell products using replication deficient adenovirus.
One aspect of the invention is a method of purging tumor cells from a stem cell product (SCP) having from approximately 2xc3x97107 to 3xc3x97108 nucleated cells/ml (NC/ml), the method comprising the co-incubation of the stem cell product with a replication-deficient, non-integrating adenovirus (rAd) at a particle number: nucleated cell (PN:NC) ratio of approximately 2,500:1 to 250,000:1 for approximately 4 to 24 hours. In some embodiments, the PC:NC ratio may be 25,000:1 to 250,000:1 or 2,500:1 to 25,000:1. In an embodiment the co-incubation time is approximately 4 to 16 hours. In an embodiment the co-incubation is performed in a total volume of about 0.1 to 2 ml and may be performed in a total volume of about 0.1 to 1 ml. In an embodiment the SCP may be derived from bone marrow, peripheral stem cells, or mobilized stem cells, and may be enriched for CD34+ cells. In an embodiment the tumor cells are carcinoma cells or hematopoietic tumor cells.
In an embodiment rAd comprises a DNA sequence encoding a cytotoxicity inducing factor (CIF), such as an apoptosis inducing tumor suppressor gene, a cytotoxic gene, a suicide gene, or a toxin gene. The rAd may be a recombinant adenovirus, such as a type 5 adenovirus.
Another aspect of the invention is a method of treating an individual having a disease which is treated by myeloablative therapy and stem cell rescue using a purged product the method comprising (a) the removal of a stem cell product from a patient in need of such treatment, (b) purging the stem cell product using a replication-deficient, non-integrating adenovirus to generate a purged product, and (c) reinfusing the purged product of (b) into the patient.
Another aspect of the invention is a kit for purging a stem cell product of tumor cells, the kit comprising a replication-deficient, nonintegrating adenovirus of a known total particle number/ml, and optionally containing at least one of a buffer for adjusting the concentration of the adenovirus, a buffer for adjusting the concentration of the adenovirus, and directions for use of the kit.